This application claims the priority of Korean Patent Application No. 2002-47518, filed Aug. 12, 2002 in the Korean Industrial Property Office, which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a precursor for hafnium oxide layer and a method for forming a hafnium oxide layer using the precursor, and more particularly, to a precursor for a hafnium oxide layer that can be deposited at a low temperature and a higher rate with enhanced electrical characteristics and step coverage, a method for forming a hafnium oxide layer using the precursor, a capacitor and a transistor using the hafnium oxide layer formed by the method, and an electronic device using the capacitor and/or transistor.
2. Description of the Related Art
Dielectric materials are used in the formation of gate oxide layers or capacitor dielectric layers of semiconductor (memory) devices. The characteristics of the dielectric materials greatly affect the operational characteristics of the devices. Conventionally, a silicon oxide layer has been widely used as a gate oxide layer or a capacitor dielectric layer. However, as semiconductor devices are more highly integrated, research on a hafnium oxide layer, a zirconium oxide layer, an aluminum oxide layer, and a strontium titanate layer, which have a high dielectric constant, is done. Among those promising dielectric materials, hafnium oxide (HfO2) is expected to be the most useful in next-generation highly integrated semiconductor memory devices because it has a high band gap energy of 5.9 eV and a dielectric constant of 20 or greater, and provides good interfacial stability between silicon and Hf—O.
The hafnium oxide layer can be deposited by a variety of conventional methods, for example, sputtering, chemical vapor deposition (CVD), or atomic layer deposition (ALD). Due to the requirement for excellent step coverage in more highly integrated devices, the ALD method becomes more interesting. However, a desired level of step coverage cannot be satisfied with the ALD method where a thin film of a thickness level of atomic layers is repeatedly deposited.
Also, the rate at which the hafnium oxide layer is deposited is slow. Accordingly, silicon deposited as a lower electrode is oxidized into SiO2 during the deposition of the hafnium oxide layer. As a result, as is widely known, the dielectric characteristics cannot be achieved with only a single HfO2 layer. For example, when a HfO2 layer is deposited using HfCl4, which is most widely used, as a Hf source, the deposition rate of the HFO2 layer is as low as 0.07 nm/cycle, although it is theoretically as high as 0.11 nm/cycle or greater. A reason for the low deposition rate is considered to be due to the repulsive force between adjacent Cl atoms in the molecules, which reduces the amount of the HfCl4 deposited in a unit area.
HfCl4 as a major Hf source is in a solid state at room temperature and has a low vapor pressure of 0.1 torr at 200° C. Accordingly, when a bubbling method is applied, a very small amount of the HfCl4 can be provided into a reactor for each cycle. Therefore, when the Hf source is applied to form a three-dimensional capacitor, surface-area widens too far and poor step coverage is inevitable.